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Marine Engineering

Study material and Knowledge files for the Marine Engineers like Motor,Naval Architecture,Marine Engineering Practice,etc.

Ship-generated waves can make bad effects on offshore structures. A numerical model is presented for evaluating the forces exerted on a nearby floating structure by ship generated waves. The ship waves were modeled using Michell thin-ship theory (Wigley waves), the forces were computed using a boundary element method in the time domain, and the motions of the offshore structures were evaluated using the equation of motion of the floating body, and predicted using the fourth-order Runge-Kutta method. The numerical method was validated by comparing its results to those of frequency-domain methods reported in the literature. It was then applied to calculate the force of ship waves on a floating box. The ship's speed, dimensions, and distance were varied. The numerical results indicate some useful rules for varying these factors.
THE world's marine coatings producers, dominated by European companies with the most effective technologies for preventing fouling of ships' hulls, are still striving to flnd a replacement for tributylin (TBT), a tin-based substance that caused environmental havoc before heing banned globally three years ago. TBT was a highly effective active ingredient for killing creatures that foul the hulls of ships and various other marine structures. It was first introduced in marine coatings in the 1960s and was soon accounting for more than two-thirds of the global market.
A consistent near-field linearized potential-flow analysis of a surface-effect ship traveling at a steady speed in laterally restricted water of finite depth is described. Additionally, the influence of seals, in terms of their drag and lift on the vessel, is included in the theory. The predicted results include the sinkage and trim, the resistance components, and the profile of the free surface of the water along the sidehulls. These predictions are compared with the corresponding results measured on a towing-tank model. It is demonstrated that the inclusion of the influence of the seals substantially improves the numerical predictions for the sinkage and trim. Good agreement is achieved for the total resistance provided a frictional form factor of 1.306 is used. The correlation between theory and experiment for the profile of the free surface is high, except in the vicinity close to the bow, where the nonlinear effects in that region are strong.
DAVE CULP HAS A RADICAL VISION. He sees enormous diesel ships,cargo carriers and supertankers and luxury liners, vessels weighing tens of thousands of tons hitched to giant kites and towed on their courses by ocean winds. He sees the ancient kite becoming a crucial technology of global trade, a tool to move goods and passengers cleanly and swiftly around the world. It's a romantic idea. But Culp, a designer of recreational kitesails who has become the chief American proponent of a return to sail power, is far from alone. Last year the German government handed almost $1 million to a start-up, SkySails, that has precisely the same long-term aim as Culp's company, KiteShip: to retrofit a substantial segment of the world s commercial fleet with huge fuel saving kites. The large Swedish shipping company Wallenius Wilhelmsen recently announced plans to build the first zero-emissions cargo vessel, featuring 45,000 square feet of rigid sail.
In order to study the dynamic behavior of ships navigating in severe environmental conditions it is imperative to develop their governing equations of motion taking into account the inherent non-linearity of large-amplitude ship motion.The purpose of this paper is to present the coupled non-linear equations of motion in heave,roll,and pitch based on physical grounds.Theingredients of the formulation are comprised of three main components. These are the inertia forces and moments, restoring forces and moments, and damping forces and moments with an emphasis to the roll damping moment. In the formulation of the restoring forces and moments, the influence of large-amplitude ship motions will be considered together with ocean wave loads. The special cases of coupled roll-pitch and purely roll equations of motion are obtained from the general formulation.
Power-augmented ram wings can be used for very fast transportation of heavy cargo over water and relatively flat solid surfaces. This article describes a coupled aerohydrodynamic model for a ram wing in steady forward motion. Effects of a finite wingspan and finite Froude numbers are accounted for by the extreme ground effect theory for airflow and a linearized potential flow theory for water. Representative results showing the influence of several variable parameters of the vehicle geometry and operational regimes are demonstrated for a selected ram-wing configuration. The developed method can be applied for modeling of airborne lifting surfaces operating in the strong ground effect on a variety of fast marine craft.
Over the last few years fast-sampling ultra-violet (UV) imaging cameras have been developed for use in measuring SO2 emissions from industrial sources (e.g. power plants; typical fluxes ∼1–10kgs−1) and natural sources (e.g. volcanoes; typical fluxes ∼10–100kgs−1). Generally, measurements have been made from sources rich in SO2 with high concentrations and fluxes. In this work, for the first time, a UV camera has been used to measure the much lower concentrations and fluxes of SO2 (typical fluxes ∼0.01–0.1kgs−1) in the plumes from moving and stationary ships. Some innovations and trade-offs have been made so that estimates of the fluxes and path concentrations can be retrieved in real-time. Field experiments were conducted at Kongsfjord in Ny10 Ålesund, Svalbard, where emissions from cruise ships were made, and at the port of Rotterdam, Netherlands, measuring emissions from more than 10 different container and cargo ships.
THE FUTURE is uncertain. The U.S. Navy is tasked with fulfilling its missions in an environment of evolving threats and a corresponding rapidly evolving mission system technology base. Affordability of our fleet is also of paramount concern. An alternative to the traditional approach of optimizing a point ship design to meet a specific set of fixed requirements is needed to maintain a sufficiently sized and relevant naval fleet that can be built and supported within the available budget.
The main objective of this paper is to enhance the overall performance of Marine Diesel Engine power plant on board passenger ships through a proposed fresh water generator and combined heat and power system which minimize the fuel emission and improve the maritime supply chain transportation network. Fresh water produced will be used for drinking, cleaning and washing purposes contributing to the high demand consumption particularly on board passenger ships. The main idea for proposed fresh water generator is to use the waste heat recovered from scavenging air to provide the heat required to evaporate sea water under vacuum converting it into steam. Energy conservation system for exhaust gases in container ships has a lot of advantages which include, reducing fuel consumption for ships, increasing the overall efficiency, reducing the pollutant emissions which go out into the atmosphere, and saving lost money. Which minimize the fresh water supply by 8 tons/day. T
Abstract: To maintain an optimum balance between security and efficiency of maritime transport in shallow waterways with a lot of deepdraft ship traffic such as in the St. LawrenceWaterway, it is particularly important to accurately estimate the ship squat, which is the reduction of the underkeel clearance between a vessel at rest and in motion. Recently, a squat model based on a regression tree was developed. The skill of this model to predict squat in the St. Lawrence Waterway exceeded the performance of 10 empirical models commonly used by the operational and regularity agencies. Although this approach is promising, two main problems were noticed: (1) the predictions obtained by the regression tree are not smooth and (2) the squat predicted with this model is not always monotonically increasing with ship speed (Froude number). In this paper, a stepwise regression tree algorithm is used to model squat.
In this work we were interested in the use for the localization of the ship noise sources in the water environment. Particular interest was dedicated to identifying of narrow band contribution to the total spectra of the ship hydroacoustic noise. The analyses were performed in time and frequency domain. The diesel engine, the electric motor and the propeller have notably been studied and the different frequencies connected to these devices have been listed. Extensive measurements were made of the underwater radiated noise of K1 and K2, small vessels powered by an electric and diesel engines. The discrete Fourier transform and the short time Fourier transform and sound intensity method were used for a precise analysis. The coherence function was also performed to associate each component of underwater noise with the vibrating part of the engine, which generates it.
Maintenance of the ship machinery is based on the maintenance plan built on data supplied by the manufacturer. The greatest attention is oriented towards maintaining the components of marine systems that are of great signifi cance for safety and operation. Marine hydraulic systems and equipments are not important for the safety and operation of the ship machinery and are usually omitted from the periodic systematic review. For this reason, this paper presents some of the failures of the hydraulic systems and equipments and the ways of correcting them. The main causes of the hydraulic systems failures can generally be: design, production and exploitation. The appearance of noise, high fl uid temperature and power decrease in the ship’s hydraulic system are interrelated phenomena that lead to failure. As it is displayed, damages of pistons of the axial-piston hydraulic machine appear due to the viscosity decrease below the limiting values.
Hull form optimization from a hydrodynamic performance point of view is an important aspect in preliminary ship design. This study presents a computational method to estimate the ship seakeeping in regular head waves. In the optimization process, the genetic algorithm (GA) is linked to the computational method to obtain an optimum hull form by taking into account the displacement as a design constraint. New hull forms are obtained from the wellknown S60 hull and the classical Wigley hull taken as initial hulls in the optimization process at two Froude numbers (Fn=0.2 and Fn=0.3). The optimization variables are a combination of ship hull offsets and main dimensions. The objective function of the optimization procedure includes the peak values for vertical absolute motion at the centre of gravity (CG) and the bow point (0.15Lwl) behind the forward perpendicular (FP).
In marine applications, the gas turbine is usually driving the propellers of ships or ferry. The major advantage of gas turbines over conventional steam turbines or marine diesel main engines is their excellent power to weight ratio. However, the increasing price of fuel determined a lot of ship companies to return to old marine diesel engines. Fuel cells power systems have attracted attention due to their potential for high efficiencies, low emissions, flexible use of fuels and quiet operation. These benefits recommend fuel cells for the marine use. This paper deals with the exergy analysis applied to gas turbines in order to assess exergy losses in processes developed in the combustion chamber and in a fuel cell replacing it, in order to measure thermodynamic efficiency. It is found that exergy losses in the improved gas turbine are lower compared to the traditional one.
It has long been recognized that fish can avoid approaching vessels and that these behaviours can bias fishery surveys. Underwater noise is considered the primary stimulus, and standards for research vessel noise have been established to minimize fish reactions. We review the literature on fish reactions to vessels appearing since these recommendations were made, focusing on acoustic surveys, and compare how fish react to noise-reduced and conventional vessels. Reactions to approaching vessels are variable and difficult to predict. However, the behaviour can bias acoustic abundance measurements, and should be considered when performing acoustic surveys. The few comparisons of acoustic abundance measurements from noise-reduced and conventional vessels are contradictory, but demonstrate that the sound pressure level, on which the noise-reduction criterion is based, is insufficient to explain how fish react to survey vessels.
Fault diagnosis system of ship power system can assist the crew to deal with faults, shorten the processing time, and prevent faults expanding. Multiagent technique is adopted for the fault diagnosis system. Ship power system is divided into several feeder units. Each one is abstracted as a regional feeder agent (FED-Agent). A multiagent fault diagnosis system is established with FEDAgent and other functional agents. Considering of the characteristics of agent, themultiagent systemprocesses both autonomy and interactivity. It can solve fault diagnosis problem of ship power system effectively.
A diesel propulsion plant for large ships is a very complex and high risk system with strong demands for its reliability. Strict requirements are to be imposed on the marine diesel engine speed control in all working conditions. This paper deals with the problem of tuning the engine speed controller parameters. A very effective and practical experimental tuning method, based on the experience of engine experts, has been proposed and tested during the final testing of a large marine 2-stroke slow speed diesel engine on a test bed. The digital engine speed controller with an electrical synchronous servo motor has been used as the fuel actuator. Several scenarios of the engine speed controller tuning and testing with the fuel actuator and the engine speed response are given in the paper for illustration purpose.
Open ships inherently possess low torsional rigidity because of their open deck structural configuration. Some of the structural failures for open ships are caused by wave-induced torsional moment in combination with other load components in oblique seas. Relatively few experimental results about horizontal bending and torsional moments in oblique seas have been published, however. Further, test data for vertical shear force and vertical bending moment in oblique seas are quite scarce. A backbone model has been recently tested by the Center for Ships and Ocean Structures (CeSOS) in the towing tank and ocean basin at the Marine Technology Center. The model consists of 15 box-shaped segments, in addition to bow and stern segments, which are interconnected by an aluminum beam on the top. Model tests in oblique seas without fonward speed were first carried out to provide basic comparisons. Tests in head and oblique seas with speeds were then conducted in regular waves.
In practice the severity of ship response is measured by high quantiles of long-term distribution of the response. The distribution is estimated by combining the short-term distribution of the response with a long-term probability distribution of encountered sea states. The paper describes an alternative approach, the so-called Rice’s method, based on estimation of expected number of upcrossings of high levels by stress during 1 year. The method requires description of long-term variability of the standard deviation, skewness, kurtosis, and zero upcrossing frequency of ship response. It is assumed that the parameters are functions of encountered significant wave height, heading angle, and ship speed. The relation can be estimated from the measured stresses or computed by dedicated software assuming rigid ship hull model. Then Winterstein’s transformed Gaussian model is used to estimate the upcrossing rates of response during a sea state.
Regional and global air pollution from marine transportation is a growing concern. In discerning the sources of such pollution, researchers have become interested in tracking where along the total fuel life cycle these emissions occur. In addition, new efforts to introduce alternative fuels in marine vessels have raised questions about the energy use and environmental impacts of such fuels. To address these issues, this paper presents the Total Energy & Emissions Analysis for Marine Systems (TEAMS) model. TEAMS can be used to analyze total fuel life cycle emissions and energy use from marine vessels. TEAMS captures “well-to-hull” emissions, that is, emissions along the entire fuel pathway, including extraction, processing, distribution, and use in vessels.
Golden Bollard 2017


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